Plaque testing

Figure 8,10 illustrates the general configuration for testing a film s puncture resistance. We can perform this test in a number of ways. The probe may be attached to the crosshead of a universal testing machine, similar to the one illustrated in Fig. 8.3. We drive the probe down through the film at a constant speed, while recording the force. Alternatively, we can perform an impact puncture test, in a similar fashion to impact plaque testing.

Flavan 4.44), which is the parent of innumerable colouring substances in fruits and flowers, is slightly active against 20 strains of common-cold virus in plaque tests. The highly lipophilic 4, 6-dichloro-derivative is much more active. How to administer such a water-insoluble substance effectively to human volunteers presented a problem but it does inhibit RNA synthesis in the parasitized cell, and the therapeutic index (mouse) is exceptionally high (Bauer etal., 1981). 

The objective of the current study was to compare the anti-psoriatic effect of six topical producfs using a modified version of the original psoriasis plaque test with emphasis on the predictive capacity of fhis model. Validation of the use of immunohistochemical and histological scoring of biopsy materials, in conjxmction with chemical scoring, in the prediction of anti-psoriatic effecfs was an additional objective [S ]. 

This study has demonstrated that the modified psoriasis plaque test can provide a relatively quick and effective method to evaluate the anti-psoriatic effect of several topical treatments in small cohorts and that, by combining clinical scoring and histological assessment, more accurate prediction of the antiseptic affect can be made. Furthermore... 

QueiUe-Roussel C, Hoffmann V, Ganslandt S, Hansen KK. Comparison of the anti-psoriatic effect and tolerability of calcipotriol-containing products in the treatment of psoriasis vulgaris using a modified psoriasis plaque test. Clin Drug Invest 2012 32(9) 613-9. 

The results of impact plaque testing depend on the configuration of the support and tup employed. The results obtained with a given configuration are not directly comparable with those of other configurations. The data generated by this test are useful for ranking samples that have been tested under identical conditions and fail in a similar manner. Such data may not be directly relevant to end use applications. 

Tensile impact testing is used to determine the impact resistance of samples that are too thin or too flexible for impact beam or impact plaque testing but cannot be considered films. It involves strain rates that are intermediate between those used for impact beam testing and those used for conventional tensile testing. This procedure is performed according to ASTM Method D 1822. 

Laser ablation systems hold considerable promise if restenosis (reblocking of the arteries) rates are reduced. The rate as of 1995 is 30%, typically within six months. Mechanical or atherectomy devices to cut, shave, or pulverize plaque have been tested extensively in coronary arteries. Some of these have also been approved for peripheral use. The future of angioplasty, beyond the tremendous success of conventional balloon catheters, depends on approaches that can reduce restenosis rates. For example, if appHcation of a dmg to the lesion site turns out to be the solution to restenosis, balloon catheters would be used for both dilating the vessel and deUvering the dmg. An understanding of what happens to the arterial walls, at the cellular level, when these walls are subjected to the various types of angioplasty may need to come first. 

Abrasive. Dentifrices have the unique ability to remove extrinsic tooth stains, which are caused by agents such as berries, tea, smoking, antibiotics, and certain bacteria as they attach to the dental pellicle. These stains can be removed only by abrasive cleaning a toothbmsh alone is not adequately effective. It has been shown that only 4% of a test population were able to maintain thein teeth in an acceptably stain-free state without an abrasive and that 18% of the population were "heavy" stainers (2). However, colored materials found in dental plaque are removable without abrasives. 

An antimicrobial agent that reduces dental plaque and can be deUvered effectively from toothpaste is a combination of Triclosan [3380-34-5] (0.2% in the toothpaste) and zinc citrate (0.5%) (7). This agent influenced plaque accumulation and reduced the incidence of gingival bleeding in clinical tests. Additional dentifrices for improved gingival health are in the offing. 

In the procedure for the surface test (313), the vims is grown in a monolayer of baby hamster kidney cells and incubated in Eagles medium supplemented with tryptose phosphate broth and calf semm. After separation of the vims from the cells by sonification and centrifugation, amounts of the suspension containing 3 x 10 plaque-forrning units are dried on coversHps. The inoculated coversHps are placed in 5 ml of the disinfectant for 1, 5, or 10 min, then rinsed, sonicated, and assayed. 

Rockwell hardness Sheets or plaques at least 0.25 in. thick are used. This thickness may be built up of thinner pieces, if necessary. A steel ball under a minor load is applied to the surface of the specimen. This indents the specimen slightly and assures good contact. The gauge is then set at zero. Basically the major (higher) load is applied for 15 seconds and removed, leaving the minor load still applied. The indentation remaining after 15 seconds is read directly off the testing equipment dial. 

Elastomer samples are cast in molds, the size and shape of which depend on its purpose. Samples for physical properties can be produced using a custom-made book mold designed to create a thin sheet (0.1 in.) containing premolded test parts, such as those for die-C tear, flexural modulus, and so on. Alternatively, a flat plaque mold may be used to create a 6 x 6 x 0.1-in. sheet from which may be cut samples for testing. Thicker samples for hardness measurements may... 

The further allergologic workup is recommended should be performed within 6 months after the reaction [13]. Both delayed IDTs and patch tests are frequently positive, when read after 48 and 72 h (in case of local pruritus or erythematous plaques optionally at other time points, e.g. 24 h, 96 h). Since some patients tested positive with only one of these tests, it is recommended to use both tests in parallel to enhance test sensitivity (table 3). Patch tests should be conducted with undiluted RCM, whereas 10-fold diluted products in physiologic saline had been recommended when performing delayed IDTs. IDTs and late readings with undiluted RCM may be discussed in non-severe reactions to increase sensitivity, however this has not been evaluated in a sufficient number of controls. A panel of several different RCM should be tested to identify skin test-negative substances. 

Plaque assays, at present, apply to only a very limited number of viruses, e.g. poliovirus, herpes virus, human rotavirus. The principle ofthese assays is as follows test virus is dried on to coverslips which are immersed in various concentrations oftest disinfectant... 

For assaying herpes virus, monolayers of baby hamster kidney (BHK) cells are used. Virus titre is expressed as the number of plaque-forming units (pfu) per millilitre before and after exposure to a disinfectant, so that the virucidal efficacy of the test agent can be determined. A diagrammatic representation is given in Fig. 11.7. 

Yellow fevert Aqueous homogenate of chick embryos infected with attenuated yellow fever virus 170 1 Centrifugation to remove cell debris 2 Freeze drying Infectivity-titration in cell cultures by plaque assay Tests to exclude extraneous viruses... 

Perry, EK, Tomlinson, BE, Blessed, G, Bergmann, K, Gibson, PH and Perry, RH (1978) Correlation of cholinergic abnormalities with senile plaques and mental test scores in senile dementia. Brit. Med. J. 2 1457-1459. 

Diagnosis of psoriasis is usually based on recognition of the characteristic plaque lesion, and not based on lab tests. 

An important validation of the mice that overexpress human mutant 3APP as a platform for testing therapeutics targeting 3-peptide deposition has been provided by the Elan company, using their PDAPP mouse [146]. Immunization of the mice, either at an early age or after plaques had formed, resulted in clearance of immunoreactive plaques and peptide from the subjects brains. Although the elucidation of the mechanism explaining... 

We test the impact resistance of polymer plaques using the configuration shown in Fig. 8.8. We subject circular injection molded plaques to the shock of a falling weight with a hemispherical impacter. This test is also known as the Dart Drop Test . Samples can fail in a brittle or a ductile manner. Brittle samples often shatter. Ductile samples can split or a small disk may be punched out of their center. This test provides results that are analogous to those obtained from un-notched impact beam testing. 

The three polymers that were chosen for study, e.g. PMMA (2), BPDN (3), and Hytrel (4), were selected because they represent a wide range of viscoelastic materials. These materials were processed into plaques. The plaques were annealed at 12S°C between highly polished chrome plated flat plates and cooled slowly to minimize the effects of residual stresses. Viscoelastic measurements were made under conditions cited above on two test specimens that were cut from... 

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